The proposed research involves the development of adenosine cyclic 3',5'-phosphate (cAMP) analogs that preferentially activate Type I cAMP-dependent protein kinase (cAKI). Three classes of cAMP analogs specifically activate cAKI, i.e., those with (a) electron-withdrawing 2-substituents, (b) a modified electronic character in the pyrimidine ring, and (c) negatively charged 8-substituents. The research will also involve the development of cAMP analogs that preferentially activate Type II cAMP-dependent protein kinase (cAKII). Analogs with moderately sized or sterically hindered hydrophobic 2-substituents and large hydrophobic or (N-alkyl- and N-arylcarbamoyl) N6-substituents have this specificity. The leads will be further developed by designing and synthesizing "second generation" analogs of these types and examining them for their abilities to preferentially activate either cAKI or cAKII. The analogs that preferentially activate cAKI or cAKII will be examined for their ability to compete for (3H)-cAMP binding to Site 1 and Site 2 on either isozyme. The proposed investigation will be extended to the development of cAMP and guanosine cyclic 3',5'-phosphate (cGMP) analogs that activate both cAK(I and II) and cGMP-dependent protein kinase (cGK). Three classes of analogs are known to have this property; they are 1,N6-etheno-cAMP derivatives, 1,N2-etheno-cGMP derivatives, and N1-substituted-cAMP and inosine cyclic 3',5'-phosphate (cIMP) derivatives. "Second generation" analogs based on these leads will be designed, synthesized, and examined for their ability to activate cAK(I and II) and cGK.